IMO they are two totally different engines, 24v is smooth, light, refined and efficient, they are a good engine but they need to be wound right up before they get moving properly.
An M30 is a noisy old slugger, big cc with 2 valve head design, heavy, late 60's roots etc..but IMO they are more fun to drive on the road!
Power delivery on them is nuts, standard M30's make about 200 lb ft @ 1.5-2k and you dont have to wait for the power to 'come on. It will pull out of a corner hard from 2k and rev right up to 6k with pretty much a constant wall of torque. A M52 wont, stamp on the accelerator at 2k and nothing really happens till round 5k.
I do need to get my E30 weighed again now its M52'd but in all honesty it dont really feel any different on the road, infact when it was M30'd the car felt more planted! especially at speed!
If i had 2 E30's side by side one M52'd and one M30'd and wanted to go for a blat about...
Id grab the keys to the M30.
However that quote is if both engines are in fine fettle and still make factory power, many M30's dont
